STRUCTURAL MODIFICATION OF SERUM VITAMIN-D-3-BINDING PROTEIN AND IMMUNOSUPPRESSION IN AIDS PATIENTS

A serum glycoprotein, vitamin D-3-binding protein (Gc protein), can be converted by beta-galactosidase of stimulated B lymphocytes and siali dase of T lymphocytes to a potent macrophage-activating factor (MAF), a protein with N-acetylgalactosamine as the remaining sugar moiety. Th us, Gc protein is a precursor for MAF. Treatment of purified Gc protei n with immobilized beta-galactosidase and sialidase generates an extre mely high-titered MAF (GcMAF). When peripheral blood monocytes/macroph ages of 46 HIV-infected patients were treated with GcMAF (100 pg/ml), the monocytes/macrophages of all patients were efficiently activated. However, the MAF precursor activity of plasma Gc protein was low in 16 (35%) of these patients. Loss of the MAF precursor activity appeared to be due to deglycosylation of plasma Gc protein by alpha-N-acetylgal actosaminidase found in the patient blood stream. Levels of plasma alp ha-N-acetylgalactosaminidase activity in individual patients had an in verse correlation with the MAF precursor activity of their plasma Gc p rotein. Thus, precursor activity of Gc protein and alpha-N-acetylgalac tosaminidase activity in patient blood can serve as diagnostic and pro gnostic indices.